As integrated circuits (IC) feature sizes shrink, problems of increased resistance and resistance-capacitance (RC) coupling offset any speed advantage derived from the smaller device size, limiting improvement in device performance. Ways to improve device performance and reliability include using highly conductive metals, such as copper, and employing lower dielectric constant (low-k) materials.
Low-k materials are semiconductor-grade insulating materials that have a dielectric constant (“k”) lower than that of silicon dioxide SiO2, i.e., 3.9. With more and more advanced technology needs, ultra low-k dielectric (ULK) materials having a k less than 2.5 are used. ULK dielectrics can be obtained by incorporating voids within a low-k dielectric, creating a porous dielectric material. Applications of ULK dielectrics include back end of line (BEOL) interlayer dielectrics (ILDs).